@Misc{BVMC:260230, title = {Homes forts, al front : P.S.U.}, publisher = {Barcelona : Sindicat de Dibuixants Professionals U.G.T., [entre 1936 i 1939] (Graf. Ultra)}, year = {1939}, url = {https://www.cervantesvirtual.com/obra/homes-forts-al-frontpsu} }